The present invention relates to the fabrication of electronic modules to be integrated into an electronic card, such as a smart card or an electronic label.
The electronic module in a smart card or the like includes at least one microcircuit and an interface which can be a contact terminal assembly in the case of conventional contact-type smart cards or one or more antennas providing contactless communication in the case of contactless smart cards and electronic labels. In the case of hybrid smart cards, the interface includes a contact terminal assembly and an antenna.
One standard process for fabricating smart cards produces electronic modules in series on a continuous support film which is then cut up to fix the modules into a cavity formed in the body of the card. To be more precise, microcircuits or chips are glued to the support film carrying an interface and the connections from the microcircuit to the interface are then made. The connections and the chip are then covered with a coating, in particular a drop of thermosetting resin providing mechanical protection.
This is followed by an operation of fixing the electronic module into the cavity in the card, usually referred to as xe2x80x9ccardingxe2x80x9d. An adhesive such as a cyanoacrylate glue or even a heat-activated adhesive can be placed in the cavity for this purpose. Alternatively, a heat-activated adhesive can be hot-laminated onto the film after the coating operation and before cutting out the module. The adhesive is then re-activated by hot pressing once the module has been placed in the cavity.
The protective resin for small chips is usually deposited directly onto the support film. In contrast, for large microcircuits, and in particular rectangular ones, in order to obtain a reproducible shape it is necessary to delimit the surface of the drop of resin by means of a xe2x80x9cbarrierxe2x80x9d deposited around the electronic module. The use of a barrier facilitates depositing the resin and in some cases removes the need for the milling operation that is otherwise necessary to obtain the final thickness of the module.
The barrier can be a polymer (epoxy, silicone, polyester) barrier deposited by means of a syringe (xe2x80x9cdispensedxe2x80x9d) or by screenprinting. The barrier can instead be a pressed metal frame glued to the support film.
The technique using a barrier has a number of drawbacks. Firstly, its cost is relatively high and adds to the unit cost of the electronic card. In the case of a silicone barrier, there are secondary effects (pollution of the surfaces to be glued). The operation of depositing the resin must be carefully controlled to prevent the resin overflowing, which constitutes a cause of rejection. Finally, it is difficult to dispense with the milling operation in the case of thermosetting resins.
To avoid the above drawbacks, another process includes steps of cold laminating a perforated adhesive tape onto the support film, casting a resin in the openings formed by the perforations in the adhesive tape by a process referred to as xe2x80x9cshutteringxe2x80x9d, setting the thickness by stamping, if necessary, and peeling off the adhesive tape.
This process uses a particular consumable, namely the adhesive tape, which is of non-negligible cost. Also, to reduce the cost of this technology, the adhesive tape must be cut and applied and the resin must be deposited and the tape removed on the same machine. What is more, not even the slightest residue of adhesive on the film can be tolerated as this may compromise the xe2x80x9ccardingxe2x80x9d operation. These two objectives are difficult to achieve with high efficiency, the slightest offset in the registration of the adhesive tape leading to a high reject rate. It is difficult to apply a cold adhesive which must be peeled off after coating without the adhesive beginning to peel in the vicinity of the cutout, which causes the resin to leak beyond the intended area.
Another technique is described in European Patent Application EP-A-0 201 952. It includes the steps of cold laminating a perforated adhesive tape onto a film that is bare and/or incorporates the chip and/or the connecting wires, said tape consisting of a mass of adhesive and a removable protective film, spraying a varnish onto the protective film coating the chip and the connections in this way, removing the protective film, which has served as a mask, cutting out the module using a punch/die-type tool and placing the module directly in the cavity.
This process is difficult to use and its mechanical reliability is debatable. During cutting, the remaining mass of adhesive may stick to the die and/or the card. A second protective film with openings corresponding to the modules is then placed over the mass of adhesive.
This process has the drawbacks of involving too many process steps and of requiring a specific consumable, in the form of the second film, and is therefore costly to implement.
The problem addressed by the invention is that of providing a simple, reliable and economic method of fabricating electronic modules for electronic cards.
The proposed solution aims not only to reduce the number of process steps but also to eliminate the use of consumables. To this end, the principle of the invention is to use the adhesive employed for fixing as a barrier to or delimiter of the coating resin.
To this end, the invention provides a method of fabricating at least one electronic module or label which is adapted to be rendered adhesive, said module or label including a support film, at least one microcircuit and at least one interface of the contact and/or antenna type connected together by connections and disposed on the support film, a coating resin protecting at least said microcircuit and said connections, said coating resin being disposed over a predetermined area, and an external activatable adhesive, said method including the following steps:
a) an insulative film is supplied including at least one contact and/or antenna type interface,
b) an adhesive tape is supplied including an activatable adhesive and a removable protective film, said tape including at least one perforation corresponding to the area of the resin on the module or label,
c) the adhesive tape is applied to the support film so that said perforation coincides with the area of the resin and said adhesive is activated so that it fixes the tape to the film, and
d) the coating resin is dispensed over the intended area at least within the perforation and in contact with the perforation, the microcircuit having been fixed to the support film connected to the interface after one of the preceding steps.
In the case of series fabrication of media provided with an electronic module, such as smart cards, or with a label, the preceding steps are performed, the support film and the tape are provided in roll form, the former including a plurality of interfaces, the latter including a plurality of perforations. The protective layer is then removed from the adhesive tape and the modules or labels are cut out before gluing them to a support of the body of the card by activating the adhesive tape.
The method according to the invention is particularly advantageous for fabricating smart cards since no dedicated consumable material is used for shuttering the resin, because the fixing adhesive is used for this purpose, and the number of process steps is reduced, because the separate operation of depositing the barrier is eliminated. Also, equipment and processes known in the art are used, which facilitates industrial application.
Minimising the number of process steps increases efficiency and reduces fabrication cost.
In the case of small microcircuits, for which a barrier is not normally used, the invention increases the volume of resin around the connecting wires and thus provides a form of packaging which is more rigid and therefore more resistant to mechanical stresses (repeated bending and twisting). This increase in reliability is achieved with no increase in unit cost.
The adhesive tape can be applied to the support film at various stages, including before gluing the microcircuits to the support film, after gluing the microcircuits and before connecting them, or after connecting them.
According to another feature of the invention, the total thickness of the adhesive tape with its external protective layer is at least equal to the intended thickness of the protective or coating resin. This enables the resin to be well contained to the required height.
The height of the barrier is preferably matched to the required height of the resin simply by varying the thickness of the protective film. Thus a very thin layer of adhesive can be used, which is preferable in particular in the fabrication of smart cards in respect of the gluing or the dynamic behaviour of the module relative to the cavity.
The coating material, which is a resin, can be dispensed in various ways, in particular by spraying, screenprinting, positive displacement dispensing (Glob Top), etc.
Positive displacement dispensing provides total control of the predetermined quantity of resin deposited and consequently its thickness. Unlike spraying, this technique provides total control over the dispensing region on the support film, in particular in the intended area within any form of perforation, barrier or delimitation.
A variant of the method of the invention differs from the previous embodiment described above in that it includes the following steps:
b) an activatable adhesive with no external protective film is supplied,
c) the adhesive is deposited so that it is distributed over all of the support film and defines a delimitation around said area and said adhesive is activated so that it adheres to the support film, and
d) the coating resin is dispensed over the intended area inside said delimitation so that the coating resin stops spreading when it comes into contact with it, the microcircuit having been fixed to the support film and connected to the interface after one of the preceding steps.
This eliminates the need for a protective film and the step of removing such film prior to fixing.
For fixing the module or antenna to a support, the method of the invention further includes a step of activating the adhesive prior to or at the same time as it is applied to and pressed onto said support.
The support is preferably a smart card or token body incorporating a cavity adapted to receive at least one microcircuit, its connections and said coating resin.
The invention also provides an electronic module or label obtained by the above methods. In the case of an electronic module including an antenna, the antenna can be formed on the rear face of the support film, in which case the module includes a second adhesive tape applied to the rear face of the support film.
This second adhesive tape constitutes a protective layer for the antenna.
The invention further provides an electronic label incorporating an electronic module in which the interface is an antenna and which is obtained by the above method. A label of this kind is constituted entirely by the electronic module, which is not xe2x80x9ccardedxe2x80x9d and retains the external protective layer. The adhesive tape is advantageously used to fix the label to a product support.
An adhesive electronic label of low unit cost is obtained in this way.
To stiffen the label, the adhesive tape can be reinforced, for example with glass fibres.
The invention further provides a smart card or token made by the methods according to the invention.
According to one feature of the invention, a standard smart card can be obtained by enclosing the module entirely within a support cavity, in particular a card body, so that the module is flush with the surface of the support.
According to one advantageous feature of the invention, the smart card or token includes a cavity adapted to receive at least one microcircuit, its connections and said coating resin and the support film is fixed to the surface of said support outside the cavity. Thus it is easy to fix a large label or module (interface with an antenna size of a few centimetres) to a card body without requiring a specific wide cavity on the support film.
The invention further provides a spool of support film carrying a plurality of modules or labels obtained by the method according to the methods of the invention.
Other features and advantages of the invention will emerge from the following description, which is given by way of illustrative and non-limiting example, and with reference to the accompanying drawings, in which: